BNC installation

On Jun 24, 7:52*pm, ContestID67 wrote:
Some comments;

1) Crimping is very much the way to go. *The heat of soldering (unless
you are very careful) can easily damage the dielectric insulator.
Invariably you are then left with a blob of solder that must be
wittled away to make thing fit. *Ugh.
2) The less expensive sub-$50 (but not dirt cheap) crimpers seem to
work fine. *Ratcheting type is highly recommended as they enforce the
correct amount of pressure. *The $200 units are made to hold up to
repeated use over years, something most of us are unlikely to need.
3) Male/Female versus Two Males with coupler (whoa!) - Stick with the
fewest possible connections. *Not only for the fact that there are
fewer things to go wrong but because each extra connection looses 2db
(rule of thumb) of your power.
4) While the boom is open, think about (if possible/practical/useful)
pulling extra air lines, coax, etc.
5) Test, test, test, test and test again before buttoning this up.
Get a professional to help out. *Well worth the expense. *Much better
now than later.
6) If you are on the scene of a boom break (I have), resisting with
all your might the temptation of cutting all the lines (air, coax) to
speed up the removal of the dead beast from the scene of the crime.
It is much better to try to take the time to disconnect things at the
cockpit end and pull them back so that any necessary splicing is done
in a easily accessible place.

Enjoy, John DeRosa

I'd raise that price limit a bit, the $50 crimpers I've seen will
not be able to crimp tight enough to achieve a proper connection. Will
it work most of the time. Sure. But I'd not want them in my aircraft.
The ratcheting type crimpers have enough jaw pressure to properly
crimp the wires (collapses a large % of the voids in the wire bundles,
creates cold welds). The ratchet makes sure you crimp it all the way.
And since many come with interchangeable dies once you need to crimp
more than one type of connector the total cost is not too bad. The
high end crimpers also have properly shaped hardened and polished
steel jaws that will crimp with high pressure without deforming the
connector.

BTW I like the Ideal Crimpmaster because they are reasonably priced ~
$50 for the bare handle with die sets ~$30-$40 each. Crimpmaster
handles and and a few dies are available at Home Depot etc. A great
web site with good selection of dies is http://www.mytoolstore.com/ideal/ide08-11.html

3M, Amp and Anderson also make great high end ratcheting crimp tools
for their line of crimp connectors. These are often ~$200-$300,
feature heavier duty construction, fine tuning of crimp pressure,
etc. Some crimp on connectors are more sensitive to others about
using the right crimp tool, e.g. some fully insulated spade/ring
connectors and Anderson PowerPole connectors.

Not that I think JJ was really posting to ask for any advice, ... but
I'd also not use a coupler. I'd just go inline M-BNC to F-BNC
connectors. It is never too late to cut the tail off again and do it
properly :-) Make sure they have gold plated pins for corrosion
resistance. I'd also put a sleeve of heat shrink over the connectors
to keep everything sealed from humidity/moisture etc. Some of the very
high-shrink type that fit over the connectors but shrink to the coax.

Darryl

"3) Male/Female versus Two Males with coupler (whoa!) - Stick with the
fewest possible connections. Not only for the fact that there are
fewer things to go wrong but because each extra connection looses 2db
(rule of thumb) of your power."

Comment: While I am not an authority on connector loss, my opinion is that
the estimated 2 db loss per connector is high. I have built an EME (Earth -
Moon - Earth) communicatons system where an extra .1 db loss is the
difference between success and failure and carefully monitored losses. It
is easy to measure the loss in connectors and it is rare that 2 db is lost
on the relatively low frequency of 123 MHz. I think the norm is .1 to .2 db
per BNC connector. However, I had a box of short BNC jumper cables
(commercially made) and about one in 10 had a 2 db loss. I have never
determined why and simply discarded the high loss jumpers.

I checked a number of source books to see if I could find any defninitive
statement about "average" loss per connector at a certain frequency, and
could not find any.

The type of BNC connectors that are assembled by screwing together are much
more likely to have high losses than a properly crimped connector.

Colin Lamb

On Jun 24, 7:52*pm, ContestID67 wrote:
6) If you are on the scene of a boom break (I have), resisting with
all your might the temptation of cutting all the lines (air, coax) to
speed up the removal of the dead beast from the scene of the crime.
It is much better to try to take the time to disconnect things at the
cockpit end and pull them back so that any necessary splicing is done
in a easily accessible place.

I too helped to retrieve a glider with a boom break. We splinted the
boom with trailer jack handles and lots of duct tape and put the
fuselage in the trailer in one piece. (Thanks to PC2 who had been
there, and done that, before.)

Andy

You make a very good point, the beast may be broken but it isn't
terminal if you use a little common sense getting it apart and back in
the box. I have seen a G-103 where the club members used a crow-bar to
get the wings off because the aft lift fitting carry-through tube was
bent and wouldn't release the wings. Bad way to go, the ship was
repairable before the club got there. I also have seen a Cirrus push-
rods cut with a hack-saw, right next to the Hotiellier rfittings. Use
a little common sense, the bird still has value. BTW, prop up the fin
and the radio may just work to get a message out. The Nimbus 3 that
was missing for 3 days at Uvalde had a good radio, battery and
antenna. All the pilot had to do was prop up the fin and talk to all
the folks that were looking for him.
JJ

Andy wrote:
On Jun 24, 7:52�pm, ContestID67 wrote:
6) If you are on the scene of a boom break (I have), resisting with
all your might the temptation of cutting all the lines (air, coax) to
speed up the removal of the dead beast from the scene of the crime.
It is much better to try to take the time to disconnect things at the
cockpit end and pull them back so that any necessary splicing is done
in a easily accessible place.

I too helped to retrieve a glider with a boom break. We splinted the
boom with trailer jack handles and lots of duct tape and put the
fuselage in the trailer in one piece. (Thanks to PC2 who had been
there, and done that, before.)

Andy

On Jun 25, 7:56*am, "COLIN LAMB" wrote:
"3) Male/Female versus Two Males with coupler (whoa!) - Stick with the
fewest possible connections. *Not only for the fact that there are
fewer things to go wrong but because each extra connection looses 2db
(rule of thumb) of your power."

Comment: While I am not an authority on connector loss, my opinion is that
the estimated 2 db loss per connector is high. *I have built an EME (Earth -
Moon - Earth) communicatons system where an extra .1 db loss is the
difference between success and failure and carefully monitored losses. *It
is easy to measure the loss in connectors and it is rare that 2 db is lost
on the relatively low frequency of 123 MHz. *I think the norm is .1 to ..2 db
per BNC connector. *However, I had a box of short BNC jumper cables
(commercially made) and about one in 10 had a 2 db loss. *I have never
determined why and simply discarded the high loss jumpers.

I checked a number of source books to see if I could find any defninitive
statement about "average" loss per connector at a certain frequency, and
could not find any.

The type of BNC connectors that are assembled by screwing together are much
more likely to have high losses than a properly crimped connector.

Colin Lamb

Colin, he was making a JOKE about various Male/Female ratios etc.
I work instrumentation on military aircraft. Mil spec connectors,
crimpers, etc. Done correctly, soldered connectors and crimped
connectors are equally good. Done badly, neither is worth the trouble
they'll cause. That said, it is EASIER to assemble a soldered
connector BADLY, so crimping (with GOOD tools) would be my choice if I
actually GOT a choice.

On Jun 25, 11:38*am, Darryl Ramm wrote:

Make sure they have gold plated pins for corrosion
resistance.
I'd also put a sleeve of heat shrink over the connectors
to keep everything sealed from humidity/moisture etc. Some of the very
high-shrink type that fit over the connectors but shrink to the coax.


Darryl - Good idea to use gold plated pins for corrosion resistance.
However,
I am unsure if I would put the heat shrink over the connectors. While
it might
keep dust and dirt out, it will also serve to keep any condensation
inside and not
allow evaporation, in effect accelerating corrosion.

Instead, I use a dielectric compound like Dow Corning #4 (http://
www.skygeek.com/dc4.html).
It keeps the moisture out, prevents corrosion and doesn't dry up. It
is also especially
good on trailer light connectors.

My $0.02.

- John "67" DeRosa

PS - If you must use heat shrink, avoid the cheap Radio Shack stuff
like the plague. It doesn't
shrink enough and becomes very stiff. Find a source for good quality
heat shrink and be willing
to pay $2-$4 per 3 foot piece.

On Jun 26, 10:40*pm, ContestID67 wrote:
On Jun 25, 11:38*am, Darryl Ramm wrote:



Make sure they have gold plated pins for corrosion
resistance.
I'd also put a sleeve of heat shrink over the connectors
to keep everything sealed from humidity/moisture etc. Some of the very
high-shrink type that fit over the connectors but shrink to the coax.

Darryl - Good idea to use gold plated pins for corrosion resistance.
However,
I am unsure if I would put the heat shrink over the connectors. *While
it might
keep dust and dirt out, it will also serve to keep any condensation
inside and not
allow evaporation, in effect accelerating corrosion.

Instead, I use a dielectric compound like Dow Corning #4 (http://www.skygeek.com/dc4.html).
It keeps the moisture out, prevents corrosion and doesn't dry up. *It
is also especially
good on trailer light connectors.

My $0.02.

- John "67" DeRosa

PS - If you must use heat shrink, avoid the cheap Radio Shack stuff
like the plague. *It doesn't
shrink enough and becomes very stiff. *Find a source for good quality
heat shrink and be willing
to pay $2-$4 per 3 foot piece.

To add one more penny's worth: If the connection is a straight
section that won't need flexibility, the dielectric compound for the
internals of the connector, then the high end heat shrink tubing with
the sealer/adhesive coating inside is the cat's meow.

My 2 cents says "use connectors with gold plated internals and leave
the BNC connection bare". This opinion gained from experience in
making thousands on BNC connections and having to leave them for a few
weeks in rain, snow and ice before doing my test. Signals on the order
of microvolts were detected most cleanly when the BNC connectors were
bare - if we used any grease, tape, shrink wrap, etc. to "protect"
them we got a noisy circuit.

-John


On Jun 27, 11:51 am, Uncle Fuzzy wrote:
On Jun 26, 10:40 pm, ContestID67 wrote:



On Jun 25, 11:38 am, Darryl Ramm wrote:

Make sure they have gold plated pins for corrosion
resistance.
I'd also put a sleeve of heat shrink over the connectors
to keep everything sealed from humidity/moisture etc. Some of the very
high-shrink type that fit over the connectors but shrink to the coax.

Darryl - Good idea to use gold plated pins for corrosion resistance.
However,
I am unsure if I would put the heat shrink over the connectors. While
it might
keep dust and dirt out, it will also serve to keep any condensation
inside and not
allow evaporation, in effect accelerating corrosion.

Instead, I use a dielectric compound like Dow Corning #4 (http://www.skygeek.com/dc4.html).
It keeps the moisture out, prevents corrosion and doesn't dry up. It
is also especially
good on trailer light connectors.

My $0.02.

- John "67" DeRosa

PS - If you must use heat shrink, avoid the cheap Radio Shack stuff
like the plague. It doesn't
shrink enough and becomes very stiff. Find a source for good quality
heat shrink and be willing
to pay $2-$4 per 3 foot piece.

To add one more penny's worth: If the connection is a straight
section that won't need flexibility, the dielectric compound for the
internals of the connector, then the high end heat shrink tubing with
the sealer/adhesive coating inside is the cat's meow.

To add one more penny's worth: *If the connection is a straight
section that won't need flexibility, the dielectric compound for the
internals of the connector, then the high end heat shrink tubing with
the sealer/adhesive coating inside is the cat's meow.- Hide quoted text -


Thanks for the comments about gold plating. It has got me thinking
(ouch).

Next question: Being a person that likes to frequent hamfests (great
stuff for electronics nerds like myself - see http://www.arrl.org/hamfests.html
for details), I see lots of RF connectors for sale. It appears that
the connector plating material of choice is not gold but silver.
Maybe it is the cost savings but it seems counter-productive to use
silver as it obviously tarnishes quite quickly (and I assume that is
bad). Being a digital (non-RF) Electrical Engineer by training I
don't know enough about the qualities of the various plating materials
to hazard an educated opinion. Any ideas?

ContestID67 wrote:

Next question: Being a person that likes to frequent hamfests (great
stuff for electronics nerds like myself - see http://www.arrl.org/hamfests.html
for details), I see lots of RF connectors for sale. It appears that
the connector plating material of choice is not gold but silver.
Maybe it is the cost savings but it seems counter-productive to use
silver as it obviously tarnishes quite quickly (and I assume that is
bad).

Tarnished silver has the remarkable property of remaining conductive, so
it doesn't cause problems. The gold flashing is usually used on the
center pins only.

And to vote with John C, my experience with ungreased, unprotected BNC
connectors sitting outside is they work well for decades if they were
properly assembled to begin with. I would not be concerned with the
connector at all inside a fuselage.

--
Eric Greenwell - Washington State, USA
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